Electrical stimulation of peripheral, central and autonomic neural structures have shown increased interest due to the potential benefits it may provide to individuals suffering from many neurological and behavioral diseases. Many of these therapies today are not well accepted or are considered last in the therapeutic options due to the invasive nature of the therapy even though the efficacy may be quite good. This has created a need for less invasive therapies that are directed toward patient and physician clinical needs.
Primary headaches are one of the most debilitating ailments that afflict millions of individuals worldwide. The specific pathophysiology of headaches is unknown. Known sources of headache pain consist of trauma, vascular, autoimmune, degenerative, infectious, drug and medication-induced, inflammatory, neoplastic, metabolic-endocrine, iatrogenic, musculoskeletal and myofacial causes. Also, even though the possible underlying cause of the headache pain is identified and treated, the headache pain may persist.
Currently, the sphenopalatine (pterygopalatine) ganglion (SPG) is a target of manipulation in clinical medicine to treat headaches. The SPG is a large extra cranial parasympathetic ganglion. It consists of parasympathetic neurons that innervate (in part) the middle cerebral and anterior cerebral blood vessels, the facial blood vessels, and the lacrimal glands. A ganglion is a mass of nervous tissue found in some peripheral and autonomic nerves. Ganglia are located on the roots of the spinal nerves and on the roots of the trigeminal nerve. Ganglia are also located on the facial, glossopharyngeal, vagus and vestibulochoclear nerves. The SPG is a complex neural ganglion with multiple connections, including autonomic, sensory and motor. The maxillary branch of the trigeminal nerve and the nerve of the pterygoid canal, also known as the vidian nerve, which is formed by the greater and deep petrosal nerves send neural projections to the SPG. The fine branches from the maxillary nerve (pterygopalatine nerves) form the sensory component of the SPG, and these fibers pass through the SPG and do not synapse. The greater petrosal nerve carries the preganglionic parasympathetic axons from the superior salivary nucleus, which is located in the Pons, to the SPG. These fibers synapse onto the postganglionic neurons within the SPG. The deep petrosal nerve connects the superior cervical sympathetic ganglion to the SPG and carries postganglionic sympathetic axons that again pass through the SPG without any synapses.
The sphenopalatine ganglion (SPG), also called the pterygopalatine ganglion, is located within the pterygopalatine fossa. The pterygopalatine fossa (PPF) is bounded anteriorly by the maxilla, posteriorly by the medial plate of the pterygoid process and greater wing of the sphenoid process, medially by the palatine bone, and superiorly by the body of the sphenoid process. Its lateral border is the pterygomaxillary fissure (PMF), which opens to the infratemporal fossa.
Treatment of the SPG is mostly performed in attempted treatments of severe headaches, such as cluster headaches or chronic migraines. Various clinical approaches have been used for over 100 years to modulate the function of the SPG to treat headaches. These procedures vary from least invasive (e.g., transnasal anesthetic blocks) to much more invasive (e.g., surgical ganglionectomy) as well as procedures such as surgical anesthetic injections, ablations, gamma knife and cryogenic surgery. Most of these procedures have very good short term efficacy outcomes (days to months), however these results are usually temporary and the headache pain returns. A chronically implanted neurostimulator apparatus designed to deliver electrical stimulation to the SPG may provide much better long term efficacy in these patients. This application details the design of a neurostimulator for this purpose.